No.Originally Posted by laxxy
I think なんで is used more or less in a formal situation.
冗談なんで and 冗談だから do convey the idea enough to understand but they do not sound natural here.
冗談 なの だ から
I'm not sure why but it should keep this construction. Neither なの nor から can be omitted from this sentence. That’s all I can say for now. Sorry.